1. Field of the Invention
This invention relates to suspension systems for trailers, tractors, and other vehicles wherein the suspension system has means for fore or aft adjustment of the axle with respect to the vehicle frame for wheel alignment.
2. State of the Prior Art
In vehicle suspensions employing vertically swingable trailing arms or conventional leaf springs with radius rods to support the axle, it is known to provide adjustment means to allow fore or aft adjustment of the axle relative to the vehicle frame. Such an adjustment is necessary during the mounting of the suspension to the vehicle and subsequently during repair or routine maintenance to assure that the axles are properly aligned with respect to the longitudinal axis of the vehicle.
Conventionally, the adjustment provision in suspension systems of this type took the form of adjusting screws, cams, turnbuckles and other like devices. Once aligned, the adjustment was locked by tightening a mechanical device to secure the assembly in its relatively aligned state. This conventional adjustment system had some undesirable characteristics: The mechanical locking devices were susceptible to loosening due to wear and usage with consequent deterioration of alignment; the mechanical locking devices were susceptible to the well-meaning tinkering of truck drivers or unqualified mechanics attempting alignment corrections by hit or miss methods; and, such mechanical locking devices generally require a plurality of parts thereby increasing the complexity, weight and cost of the suspension.
A simplified and more durable adjustment system is disclosed and claimed by Masser in U.S. Pat. No. 2,481,891. In the Masser adjustment system, elongated apertures in the form of slots are provided in the frame mounting brackets. A bolt is passed through the elongated apertures and through an aperture in the end of the trailing arm. The slots enable the trailing arm to be adjusted fore or aft relative to the vehicle frame. Plates are carried by the bolt and abut a raised lug on each side of the frame bracket. These plates are welded to the sides of the frame bracket after alignment, thereby fixing the adjustment mechanism in its aligned position. Once welded, the connection is no longer susceptible to tinkering or gradual loosening and, further, the trailing arms can be disassembled and reassembled without affecting the alignment. The Masser alignment system is a substantial improvement over the conventional mechanical adjustment locking devices. However, it requires the use of several special parts or special fittings added to conventional parts. Further, the fore or aft adjustment prior to welding, or in subsequent adjustments where the weld has been burned away, are accomplished through the rather crude and imprecise method of striking the trailing arm assembly while in a loosened condition to move the assembly in the desired direction.